Hummocky and fluted moraines in part of North-West Scotland
Abstract
This thesis is concerned with the formation and significance of
moraines produced c. 11,000-10,000 yrs. B. P. by the glaciers of the
Loch Lomond Advance. The moraines have a variety of forms but they
have previously been divided into two groups; fluted and hummocky
moraines. Fluted moraines have been shown by previous work to be
subglacial landforms produced by active ice whereas the majority of
hummocky moraines have been attributed to deposition from the surface
of stagnant ice.
The methods employed include field mapping and morphological
interpretation but the most important data are derived from measuring
the particle-size distribution, rock-type composition and other
characteristics of the till.
Groups of samples are taken from several groups of fluted
moraines. Changes in the properties of the till at different parts
of the ridge, between members of a group of ridges, and between
ridges and underlying or adjacent till are discussed. The features
studied have a variety of sizes but they are generally on a scale
that has rarely been described in previous literature, being
intermediate between large-scale and small-scale features.
Associations between fluted moraines and hummocky moraines in
the field area raised the suspicion that some of the latter may have
been formed subglacially. Detailed sampling revealed that all the
hummocky moraines studied contain a large proportion of material that
was picked up from the valley floors and carried only a short
distance during the Loch Lomond Advance. These findings together
with other evidence lead to the firm conclusion that the hummocky
moraines studied were produced by active ice. This conclusion is
accompanied by discussion of the mechanisms by and conditions under
which the moraines could have been formed and could have survived.
It is suggested that the material was, at least in part, pushed up by
the advancing ice front and subsequently passed over by the ice which
reworked it to varying degrees.